From f6f2469d4d73966eabbf366a981e161f350a43e7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sergio=20Conde=20G=C3=B3mez?= <skgsergio@gmail.com>
Date: Tue, 11 May 2021 10:24:46 +0200
Subject: [PATCH] fix: HCL "index" function now actually returns the index of
 the element (#11008)

---
 hcl2template/function/index.go      |  58 +++++++++++++
 hcl2template/function/index_test.go | 127 ++++++++++++++++++++++++++++
 hcl2template/functions.go           |   2 +-
 3 files changed, 186 insertions(+), 1 deletion(-)
 create mode 100644 hcl2template/function/index.go
 create mode 100644 hcl2template/function/index_test.go

diff --git a/hcl2template/function/index.go b/hcl2template/function/index.go
new file mode 100644
index 000000000..0cb55a747
--- /dev/null
+++ b/hcl2template/function/index.go
@@ -0,0 +1,58 @@
+package function
+
+import (
+	"errors"
+
+	"github.com/zclconf/go-cty/cty"
+	"github.com/zclconf/go-cty/cty/function"
+	"github.com/zclconf/go-cty/cty/function/stdlib"
+)
+
+// IndexFunc constructs a function that finds the element index for a given value in a list.
+var IndexFunc = function.New(&function.Spec{
+	Params: []function.Parameter{
+		{
+			Name: "list",
+			Type: cty.DynamicPseudoType,
+		},
+		{
+			Name: "value",
+			Type: cty.DynamicPseudoType,
+		},
+	},
+	Type: function.StaticReturnType(cty.Number),
+	Impl: func(args []cty.Value, retType cty.Type) (ret cty.Value, err error) {
+		if !(args[0].Type().IsListType() || args[0].Type().IsTupleType()) {
+			return cty.NilVal, errors.New("argument must be a list or tuple")
+		}
+
+		if !args[0].IsKnown() {
+			return cty.UnknownVal(cty.Number), nil
+		}
+
+		if args[0].LengthInt() == 0 { // Easy path
+			return cty.NilVal, errors.New("cannot search an empty list")
+		}
+
+		for it := args[0].ElementIterator(); it.Next(); {
+			i, v := it.Element()
+			eq, err := stdlib.Equal(v, args[1])
+			if err != nil {
+				return cty.NilVal, err
+			}
+			if !eq.IsKnown() {
+				return cty.UnknownVal(cty.Number), nil
+			}
+			if eq.True() {
+				return i, nil
+			}
+		}
+		return cty.NilVal, errors.New("item not found")
+
+	},
+})
+
+// Index finds the element index for a given value in a list.
+func Index(list, value cty.Value) (cty.Value, error) {
+	return IndexFunc.Call([]cty.Value{list, value})
+}
diff --git a/hcl2template/function/index_test.go b/hcl2template/function/index_test.go
new file mode 100644
index 000000000..5695cde7d
--- /dev/null
+++ b/hcl2template/function/index_test.go
@@ -0,0 +1,127 @@
+package function
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/zclconf/go-cty/cty"
+)
+
+func TestIndex(t *testing.T) {
+	tests := []struct {
+		List  cty.Value
+		Value cty.Value
+		Want  cty.Value
+		Err   bool
+	}{
+		{
+			cty.ListVal([]cty.Value{
+				cty.StringVal("a"),
+				cty.StringVal("b"),
+				cty.StringVal("c"),
+			}),
+			cty.StringVal("a"),
+			cty.NumberIntVal(0),
+			false,
+		},
+		{
+			cty.ListVal([]cty.Value{
+				cty.StringVal("a"),
+				cty.StringVal("b"),
+				cty.UnknownVal(cty.String),
+			}),
+			cty.StringVal("a"),
+			cty.NumberIntVal(0),
+			false,
+		},
+		{
+			cty.ListVal([]cty.Value{
+				cty.StringVal("a"),
+				cty.StringVal("b"),
+				cty.StringVal("c"),
+			}),
+			cty.StringVal("b"),
+			cty.NumberIntVal(1),
+			false,
+		},
+		{
+			cty.ListVal([]cty.Value{
+				cty.StringVal("a"),
+				cty.StringVal("b"),
+				cty.StringVal("c"),
+			}),
+			cty.StringVal("z"),
+			cty.NilVal,
+			true,
+		},
+		{
+			cty.ListVal([]cty.Value{
+				cty.StringVal("1"),
+				cty.StringVal("2"),
+				cty.StringVal("3"),
+			}),
+			cty.NumberIntVal(1),
+			cty.NumberIntVal(0),
+			true,
+		},
+		{
+			cty.ListVal([]cty.Value{
+				cty.NumberIntVal(1),
+				cty.NumberIntVal(2),
+				cty.NumberIntVal(3),
+			}),
+			cty.NumberIntVal(2),
+			cty.NumberIntVal(1),
+			false,
+		},
+		{
+			cty.ListVal([]cty.Value{
+				cty.NumberIntVal(1),
+				cty.NumberIntVal(2),
+				cty.NumberIntVal(3),
+			}),
+			cty.NumberIntVal(4),
+			cty.NilVal,
+			true,
+		},
+		{
+			cty.ListVal([]cty.Value{
+				cty.NumberIntVal(1),
+				cty.NumberIntVal(2),
+				cty.NumberIntVal(3),
+			}),
+			cty.StringVal("1"),
+			cty.NumberIntVal(0),
+			true,
+		},
+		{
+			cty.TupleVal([]cty.Value{
+				cty.NumberIntVal(1),
+				cty.NumberIntVal(2),
+				cty.NumberIntVal(3),
+			}),
+			cty.NumberIntVal(1),
+			cty.NumberIntVal(0),
+			false,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(fmt.Sprintf("index(%#v, %#v)", test.List, test.Value), func(t *testing.T) {
+			got, err := Index(test.List, test.Value)
+
+			if test.Err {
+				if err == nil {
+					t.Fatal("succeeded; want error")
+				}
+				return
+			} else if err != nil {
+				t.Fatalf("unexpected error: %s", err)
+			}
+
+			if !got.RawEquals(test.Want) {
+				t.Errorf("wrong result\ngot:  %#v\nwant: %#v", got, test.Want)
+			}
+		})
+	}
+}
diff --git a/hcl2template/functions.go b/hcl2template/functions.go
index 3ac79cfec..a85f414f0 100644
--- a/hcl2template/functions.go
+++ b/hcl2template/functions.go
@@ -63,7 +63,7 @@ func Functions(basedir string) map[string]function.Function {
 		"formatdate":         stdlib.FormatDateFunc,
 		"formatlist":         stdlib.FormatListFunc,
 		"indent":             stdlib.IndentFunc,
-		"index":              stdlib.IndexFunc,
+		"index":              pkrfunction.IndexFunc, // stdlib.IndexFunc is not compatible
 		"join":               stdlib.JoinFunc,
 		"jsondecode":         stdlib.JSONDecodeFunc,
 		"jsonencode":         stdlib.JSONEncodeFunc,